#include <iostream>
#include <algorithm>
#include <unordered_map>
#include <cstring>
using namespace std;

int main() {
    string s;
    char a;
    int sum=0;
    unordered_map<char,int> mp;
    while(getline(cin,s))
    {
        for(int i=0;i<s.size();i++)
        {
            if(s[i]>='a'&&s[i]<='z')
            {
                mp[s[i]]++;
                if(mp[s[i]]>sum){
                    a=s[i];
                    sum=mp[s[i]];
                }
            }
        }
    }
    cout << a;
    return 0; 
}